Merge branch 'jc/you-still-use-whatchanged'

"git whatchanged" that is longer to type than "git log --raw"
which is its modern rough equivalent has outlived its usefulness
more than 10 years ago.  Plan to deprecate and remove it.

* jc/you-still-use-whatchanged:
  whatschanged: list it in BreakingChanges document
  whatchanged: remove when built with WITH_BREAKING_CHANGES
  whatchanged: require --i-still-use-this
  tests: prepare for a world without whatchanged
  doc: prepare for a world without whatchanged
  you-still-use-that??: help deprecating commands for removal

git.c

@@ -646,7 +646,9 @@ static struct cmd_struct commands[] = {
 	{ "verify-pack", cmd_verify_pack },
 	{ "verify-tag", cmd_verify_tag, RUN_SETUP },
 	{ "version", cmd_version },
+#ifndef WITH_BREAKING_CHANGES
 	{ "whatchanged", cmd_whatchanged, RUN_SETUP },
+#endif
 	{ "worktree", cmd_worktree, RUN_SETUP },
 	{ "write-tree", cmd_write_tree, RUN_SETUP },
 };